1. Technical Field
The present invention relates to structure of bifurcation and crossover sites of a guideway in a guided vehicle transportation system in which a vehicle supported by traveling wheels such as rubber-tired wheels for example travels on a guideway, the vehicle being equipped with an automatic steering mechanism and a fail-safe mechanism for coping with a case malfunction has occurred in the automatic steering mechanism or strong external lateral force due to a gust of cross wind, etc. exerts on the vehicle.
2. Technical Background
In a new transit system, a vehicle which travels by rotating rubber-tired wheels is generally provided with guide wheels which are guided along a guide rail laid down on a guideway along the guideway so that the vehicle is steered to travels along the guideway, and the vehicle is usually steered mechanically.
The mechanical guide mechanism is superior in point of view of safety and reliability, however, structure of bogies to which the wheels and driving mechanism thereof are mounted becomes complicated inevitably, is increased in weight, and results in increased running costs. Further, it is necessary to lay down the guard rail having enough strength to support the guide wheels all along the guideway with high accuracy, which results in increased construction costs of the guideway.
In order to eliminate the problems mentioned above, a steering system not requiring a guide rail is proposed in Japanese Laid-Open Patent Application No. 2002-351544(patent literature 1).
The steering system of a guided vehicle disclosed in the patent literature 1 is composed such that a plurality of on-ground devices which memorize and send out information necessary for the operation of the vehicle are laid down along the whole length of the track on which the vehicle travels, the control device installed on the vehicle emits signals based on the information sent out from the on-ground devices when the vehicle travels along the track, and the vehicle is steered by the steering device installed on the vehicle in accordance with the signals. With the steering system, a guide rail for steering the vehicle is not required, construction and maintenance costs can be reduced, and also vibration and noise are reduced.
The steering system of the patent literature 1 will be explained referring to FIGS. 28a, 28b, and FIG. 29. FIG. 28a is a schematic side elevation of a vehicle provided with the conventional steering system, FIG. 28b is a schematic front elevation of FIG. 28a, and FIG. 29 is a schematic plan view of the conventional steering system. Referring to FIGS. 28a, 28b, and FIG. 29, reference numeral 03 is a vehicle used in the new tramway transit system, the vehicle 03 is a vehicle used in a new transit system and travels along a track 01. The vehicle 03 is supported on front and rear bogies 04 which supported by rubber-tired wheels 05 attached thereto. The wheels are driven by drive motors 06 and steered by actuators 07.
The steering system includes on-ground devices 02, a transmitter 09, a receiver 09, a control device 010, and a steering device 020. The vehicle is steered by turning the wheels 05. A plurality of non-exited on-ground devices 02 are laid down on the track 01 along whole length thereof at a predetermined spacing. Specific information is memorized in each of the on-ground devices. The specific information includes the discrimination number, position information, track information, and control information of the concerned on-ground device.
Position information(geographic site information) is information concerning the position of each on-ground device 02 such as the absolute coordinate point and distance from a reference point. Further, track information expressing conditions of the track at the site of each on-ground device such as the gradient, curvature, cant, ramification of the track are memorized in each of the on-ground device as necessary(the information is collectively referred to as operation information hereafter).
Although each of the on-ground devices 02 is not exited, i.e. has not been provided with power sources, it emits signals of the information memorized upon receiving electric power. The on-ground device 02 has for example an electronic circuit including ROM for memorizing operation information.
The transmitter 08 is a device for feeding electric power by means of a radio wave. The receiver 09 is a device for receiving the operation information emitted from the on-ground device 02 when the device 02 has received the radio wave. The control device 010 is a device for performing prescribed processing based on the operation information the receiver 09 received and transmitting directive signal of speed and steering of the vehicle to the drive motor 06 and actuator 07.
The steering device 020 is a device for turning the wheel 05 under the steering directive and comprises an electric or hydraulic or pneumatic actuator 07 connected to an end of an arm 011 of which the other end is supported for rotation by a pin 012 fixed to the bogie 04, a connecting rod 059, levers 056a and 056b for left and right wheel 05 respectively, and a tie rod 057 for connecting the levers.
When the actuator 07 is actuated by the steering directive from the control device 010, the arm 011 is rotated about the pin 012 and the levers 056a, 056b are turned via the connecting rod 059 and the tie rod 057 to turn the wheels 05 to the right or left.
According to the automatic steering system, the vehicle 03 is steered based on the operation information memorized in the on-ground devices 02 without using a guide rail, etc. Therefore, construction cost of the track 01 is decreased to a large extent because the guide rail, etc. is not needed. Further, as wear-out parts such as guide wheels are not used, maintenance cost is decreased, and also occurrence of vibration and noise which will occur when the guide rail and guide wheels are provided due to the contact between them can be reduced.
However, according to the automatic steering system disclosed in the patent literature 1, mechanical steering by means of the guide rail and guide wheels is not performed, and a problem of securing safety of vehicle traveling against runaway and running out of track when malfunction occurs in the steering system and under abnormal circumstances caused by strong wind, rainfall, snowfall, etc. has not been solved.
The applicant of this patent application proposed such a fail-safe mechanism in Japanese Laid-Open Patent Application No. 2006-175962 (patent literature 2) that can secure safety when malfunction occurs in the steering system with simple and light-in-weight construction.
The fail-safe mechanism is composed such that a guard groove is formed along the guideway of a guard rail havin a groove is laid down on a guideway along the guideway, and the vehicle is provided with guard wheels under the front and rear bogies supporting the vehicle body so that the vehicle travels with the guard wheels received in the groove of the guard rail. An ample clearance is secured between the periphery of the guard wheel and both side walls of the groove of the guard rail, the clearance being smaller than permissible limit clearance so that running out of the guide wheels from the groove does not occur.
When the automatic steering system functions normally, the vehicle travels with the guard wheels not contacting the side walls of the groove, however, when malfunction occurs in the automatic steering system or external force exerts on the vehicle due to a gust of cross wind for example, the guard wheels contact the side wall of the groove and running out of the guide wheels from the groove is prevented.
However, in the guided vehicle transportation system provided with the fail-safe mechanism as mentioned above, there are inevitably bifurcation site or crossover site such as Y-shaped fork roads or X-shaped fork roads, where guard rail diverges into two or more guard rails.
As the width of the groove of the guard rail is larger than the diameter of the guard wheel so that a permissible clearance is secured between the periphery of the guard wheel and side walls of the groove, for example, when the diameter of the guard wheel is 150 mm, the width of the groove of the guard rail is determined to be about 250˜300 mm. At apart where the guard rail crosses a roadbed on which the traveling wheels of the vehicle travel, the traveling wheels must cross over the opening of the groove of the guard rail. When the width of the opening of the groove of the guard rail is wide as mentioned above, tires of the traveling wheels may fall into the groove or be bitten into the opening of the groove when passing over the guide rail, suffer injury, and vibration occurs which deteriorate ride quality. Further, there is a possibility that the guard rail is damaged.